Mushroom murderer Erin Patterson never expected anyone to survive lunch - former cop

Erin Patterson never imagined that any of her victims would survive the deadly Beef Wellington lunch, says former Australian police detective Duncan McNab.

"I always thought that she had planned this case in some detail, but she hasn't planned on being caught.

"I don't think she assumed that Ian Wilkinson would survive," McNab told RNZ's Saturday Morning.

In July, Patterson was convicted of triple murder for serving Beef Wellingtons laced with poisonous death cap mushrooms to her estranged husband's family at her home in Leongatha, Victoria, in 2023.

A 12-person jury found Patterson guilty of murdering her husband Simon's parents, Don and Gail Patterson, as well as his aunt Heather Wilkinson. Patterson was also found guilty of attempting to murder Heather's husband Ian - the sole survivor of the deadly lunch.

McNab, who attended the trial, examines the case in his new book, Recipe for Murder.

During the trial, which attracted worldwide attention, it came to light that Patterson was a true crime obsessive, he said.

"She had about 400 true crime books in her library. She had podcasts in her ears pretty much throughout the entire day… that was the rhythm of her life."

If this obsession was an indicator of Patterson's intention to commit mass murder, the execution and planning of her terrible crime were riddled with mistakes, he said.

The mother-of-two must have foraged for the death cap mushrooms she used to poison her guests that day, he said.

"While we can't know that Erin got them locally, there were some death cap mushrooms spotted within 10 minutes' drive from her house on two occasions in April and in May 2023."

Mobile phone tower evidence showed Patterson's phone was in that area at the time, he said.

The dehydrator, which she used to dry the mushrooms but denied having, was found with traces of the deadly mushroom. CCTV footage captured her disposing of it at a local landfill, McNab recalled, so she was caught telling an obvious lie.

Patterson was a habitual liar, McNab said, and it was a lie that lured her lunch guests to their deaths.

"She's called the lunch, and one stage in the preparation for this, she says, 'I've got some medical news I need to share with you'.

"These are just really lovely, decent people. So, they're there if Erin needs a hand."

At the lunch, Patterson revealed that she had cancer and wanted advice on what to do about her two children.

“Erin's disclosure at that point is that she may have ovarian cancer. Ian Wilkinson, the only survivor, can't remember clearly whether it was ovarian cancer or some form of cancer.”

These "four decent people" attended Patterson's lunch so they could give her their thoughts on what to do with the children, he says. After eating the food she served, three endured terrible deaths, and another one barely survived.

The courtroom was hushed when a professor who looked after the victims in emergency care gave video-link evidence about the "mechanics of their deaths," McNab said.

“Everyone was silent. You could have heard a pin drop in the courtroom. It was terrible.”

Although it was not revealed during the murder trial, Patterson had made three previous poisoning attempts on her husband Simon, McNab said, but the reason why she fed four of his family deadly mushrooms remains "utterly elusive".

"I've met some killers in my time, and some of them just view other people as an inconvenience, a trouble to be removed."